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D Walker

Publications and source records attributed to D Walker.

At least 55 records · Page 3Linked to original sources
PubMed1997

Report of a collaborative study to establish the international standard for parvovirus B19 serum IgG.

With the introduction of commercial test kits and the wider availability of parvovirus B19 antibody testing, greater standardization is required. Moreover, with a B19 vaccine in the early stages of development, there will be long-term need of accurate measurement of parvovirus B19 antibody levels following natural infection and vaccination. A collaborative study was carried out to assess the suitability of a freeze-dried preparation designated 93/724 to serve as the International Standard for parvovirus B19 serum IgG. The proposed standard, which is a pool of sera from six U.K. blood donors, was assayed along with three coded samples. One was the proposed standard (Preparation A), one a pool of three donor sera (Preparation B) and the third an individual donor serum (Preparation C). These preparations were sent to nine laboratories in seven countries who tested them in 10 different enzyme immunoassays. There were no differences in the antibody content expressed relative to that of the proposed standard in assays using native or recombinant antigen. However, antibody was not detected in serum from an individual blood donor (Preparation C) in assays performed using kits which contained recombinant VP1 but not VP2. This highlights the differences which may be obtained in commercial kits which contain different antigens. The results of this study demonstrated that the proposed standard coded 93/724 is suitable to serve as the International Standard for parvovirus B19 serum IgG and this material has been established as the International Standard for parvovirus B19 IgG by the World Health Organization with an assigned unitage of 100 lU per ampoule. The standard, which is a pool of what can be assumed to be convalescent sera, will be suitable for standardizing diagnostic tests for use in seroprevalence studies and for assessing immunity. An additional standard will be required to standardise tests specifically for the detection of IgM and the diagnosis of acute infection.

Antibodies, Viral↗
PubMed1997

Influence of morphometric factors on quantitation of paracellular permeability of intestinal epithelia in vitro.

PURPOSE: The relative contribution of the small and large intestine to paracellular absorption is a subject of some controversy. Direct comparison of paracellular permeability in different epithelia is complicated by variations in junctional density and/or the absorptive surface area. METHODS: This study used a combination of morphometric analyses and in vitro absorption studies to define permeability characteristics in relation to the amount of paracellular pathway present in rat ileum, colon and the model epithelium, Caco-2. RESULTS: Mucosal to serosal amplification was higher in ileum (3.9) than colon (1.9) or Caco-2 (1). Tight junctional density (lp) of ileal crypts was approximately 3 fold greater (91 m/cm2) than that measured in ileal villi, colonic surface and crypt cells or Caco-2 monolayers (34-37 m/cm2). However, when the relative contributions of the crypts and villi was taken into account there was no significant difference in the mean lp per mucosal area for the three epithelia studied. Using these data to correct for morphometric differences the permeabilities of a range of small hydrophilic molecules (atenolol, D-PheAsp and PEG oligomers MW 282-634) was measured. Permeability of rat ileum and colon were virtually identical for all compounds studied. In contrast, Caco-2 monolayers showed a significantly lower permeability than intestinal tissues with the difference increasing markedly with molecular size. CONCLUSIONS: These studies suggest the importance of accounting for morphological variation when comparing the permeability characteristics of different epithelial systems.

Animals↗
PubMed1997

Influence of proxy respondents and mode of administration on health status assessment following central nervous system tumours in childhood.

Central nervous system (CNS) tumours account for 20% of childhood cancers. Survivors often experience severe physical, neuropsychological and social sequelae of the disease and its treatment. Health status assessment in these individuals is an essential clinical outcome measure, yet little consensus exists regarding the optimum methodology. The influence of proxy respondents (parents, physiotherapists and doctors) and mode of administration (home and clinic) in which assessments is performed has been evaluated in a cohort of 37 survivors of childhood CNS tumours. A health-related quality of life (HRQOL) questionnaire, incorporating the Mark II and III Health Utilities Indices, was completed at home and in clinic by patients and parents. Doctors and physiotherapists completed this questionnaire plus Lansky Play-Performance and Karnofsky Performance scores. No significant differences between raters for single attribute scores occurred either at home or in clinic, although a wide range of agreement (kappa = 0.05-1.00, percentage agreement 53-100%) between observers was revealed. Most agreement occurred between parents and patients: this was greatest on home completion (kappa = 0.48-1.00, percentage agreement 53-100%). Doctors and physiotherapists agreed less on subjective attributes (emotion, cognition and pain). Better if responses were classified as normal and abnormal. Inter-observer agreement was greater for the HRQOL questionnaire than for Karnofsky and Lansky scores. Home completion of questionnaires provides a reliable, acceptable and convenient method of assessing health status.

Adolescent↗
PubMed1997

Sequence-specific inhibition of the tumor necrosis factor-alpha receptor I gene by oligodeoxynucleotides containing N7 modified 2'-deoxyguanosine.

Tumor necrosis factor-alpha (TNF-alpha) is a highly pleiotropic cytokine produced mainly by activated macrophages. This cytokine has been found to mediate the growth of certain tumors, the replication of HIV-1, septic shock, cachexia, graft-versus-host disease, and autoimmune diseases. The binding of TNF-alpha to the p55 tumor necrosis factor receptor type I (TNFRI) is considered one of the initial steps responsible for the multiple physiologic effects mediated by TNF-alpha. The role of TNF-alpha as an inflammatory mediator through TNFRI makes both of these genes attractive targets for intervention in both acute and chronic inflammatory diseases. We have designed antisense oligodeoxynucleotides (ODNs) containing chemically modified purine and pyrimidine bases that specifically inhibit TNFRI expression and functions. These ODNs were designed to hybridize to the 3'-polyadenylation signal region of the TNFRI gene. In cell-based assays, gene-specific antisense inhibition occurred in a dose-dependent fashion at submicromolar concentrations in the presence of cellular uptake enhancing agents. Within ODN sets with a common pattern of stabilizing backbone substitution, the inhibition of the gene expression is found to be correlated with the affinity of the ODNs for their cognate mRNA target sites, providing direct evidence for an antisense mechanism of action. In addition, events triggered by the binding of TNF-alpha to TNFRI, such as the production of IL-6 and IL-8, were significantly reduced by treatment of cells with the anti-TNFRI ODN. Therefore, antisense ODNs can be used to control biologic processes mediated by TNF-alpha and may be useful as therapeutic agents to treat conditions resulting from overproduction of TNF-alpha.

Antigens, CD↗
PubMed1997

Improved oocyte quality is obtained with follicle stimulating hormone alone than with follicle stimulating hormone/human menopausal gonadotrophin combination.

The aim of this study was to compare the efficacy of pure follicle stimulating hormone (FSH) with that of FSH/human menopausal gonadotrophin (HMG) combination in downregulated cycles. A total of 357 patients was evaluated retrospectively. Sixty percent of patients in the FSH group and 55% in the FSH/HMG group were new; the others were repeat patients. Ovulation was suppressed with leuprolide acetate in all patients, followed by either FSH (n = 218) or FSH/HMG (n = 119). There was no difference in patients' age, infertility factors, number of ampoules used, length of stimulation, oestradiol levels on day of human chorionic gonadotrophin (HCG) administration, number of oocytes recovered or the number of embryos transferred. Also, nuclear maturity at aspiration and fertilization rates were not different between the two groups. FSH stimulation resulted in a significantly higher percentage of mature oocytes that showed the typical 'mature' morphological characteristics (P < 0.0001). The clinical pregnancy rates per transfer were 40 and 28% in patients stimulated with pure FSH and FSH/HMG respectively (P < 0.05). The significantly higher number of immature oocytes matured in vitro in the FSH/HMG group (P = 0.001) suggests a possible effect on in-vitro maturation, due to luteinizing hormone present in HMG. The difference in mature oocyte quality may be an important determinant in the higher pregnancy rates for the FSH-stimulated patients.

Chorionic Gonadotropin↗
PubMed1997

Intrathecal sufentanil for labor analgesia does not cause a sympathectomy.

BACKGROUND: Intrathecal sufentanil (ITS) is frequently used to provide analgesia during labor. Decreases in blood pressure and sensory changes in this circumstance suggest that ITS may have a local anesthetic effect and thus cause a sympathectomy. To determine whether ITS given to laboring women causes a sympathectomy, the authors evaluated central and lower extremity temperature changes after ITS administration. These findings were compared with those in a control group of women having spinal anesthesia with bupivacaine for elective cesarean section in whom an extensive sympathectomy was expected. METHODS: Twenty parturients classified as American Society of Anesthesiologists' physical status 1 or 2 had temperatures measured centrally, at the calf, and at the great toe at frequent intervals after receiving 10 microg ITS for labor analgesia (sufentanil group, n = 10), or hyperbaric bupivacaine 12 mg in their spinal anesthetic for cesarean section (bupivacaine group, n = 10). Calf-to-toe temperature indices (C-T) were calculated by subtracting toe temperature from calf temperature. A decrease in this index means that the toe had warmed compared with the calf and is an indication of vasodilation and a sympathectomy. RESULTS: There was no significant change in the C-T indices or central temperature in the sufentanil group, but the C-T indices and central temperature decreased significantly in the bupivacaine group. CONCLUSIONS: The decreases in the C-T index and central temperature in the bupivacaine group indicate the presence of a sympathectomy. The lack of change in the C-T indices and central temperature in the sufentanil group indicates that no significant vasodilation occurred. Therefore, the decrease in blood pressure seen after ITS administration for labor analgesia is unlikely to be the result of a sympathectomy.

Adult↗
PubMed1997

Type B lactic acidosis following cardiopulmonary bypass.

OBJECTIVE: To describe, characterize, and identify the associations of postcardiac surgical lactic acidosis occurring in the absence of clinical evidence of tissue hypoperfusion. DESIGN: The preliminary study is a report of a series of observations in 12 patients. The prospective study is also observational, involving the structured collection of hemodynamic and metabolic variables in a prescribed series of patients. SETTING: Cardiac surgical intensive care unit of a university teaching hospital. PATIENTS: Twelve patients who developed an unexplained lactic acidosis after cardiac surgery are reported in the preliminary study. The prospective study involved observations in 112 consecutive patients undergoing cardiopulmonary bypass for cardiac surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Preliminary study: Cardiac index was increased before, during and after recovery from lactic acidosis. Recovery from lactic acidosis was associated with a decrease in oxygen transport index and significant increases in oxygen consumption index and oxygen extraction ratio. PROSPECTIVE STUDY: Hemodynamic, oxygen transport, and oxygen consumption variables, together with arterial blood gas and lactate concentrations, were assessed every 6 hrs for 24 hrs after surgery. Sixteen patients developed lactic acidosis (peak lactate concentration > 5.0 mmol/L). Compared with the remainder of the patients, this subgroup had longer duration of cardiopulmonary bypass (116 +/- 31 vs. 76 +/- 31 mins, p < .01), greater intraoperative hypothermia (24.9 +/- 2.0 degrees vs. 26.6 +/- 2.3 degrees C, p < .01), more frequent requirement for vasopressor agents (14/16 vs. 35/96, p < .05) and a higher frequency of hyperglycemia (15/16 vs. 28/96, p < .01). Hemodynamic variables, including cardiac index, were remarkably similar in the acidotic and nonacidotic groups. All of the acidotic patients, in both parts of this study, recovered from their acidosis. Eleven of the patients in the preliminary study and all of the 16 acidotic patients in the prospective study were ultimately discharged from the hospital. CONCLUSIONS: This report documents the occurrence of lactic acidosis in a subgroup of patients undergoing cardiopulmonary bypass. The pathogenesis of this disorder is uncertain, but it appears to not relate to inadequate oxygen delivery. Systemic vasodilation and reduced oxygen extraction appear to be features of this disorder, which has an excellent prognosis.

Acidosis, Lactic↗
PubMed1997

Protein characterization of Australian spotted fever group rickettsiae and monoclonal antibody typing of Rickettsia honei.

Rickettsial proteins rOmp A and rOmp B exist in both Rickettsia australis and Rickettsia honei but differ in molecular weight and antigenicity; in addition, they produce distinct immunogenic responses and appear to be to conformationally dependent antigens. Species-specific monoclonal antibodies for other spotted fever group rickettsial species did not react with R. honei. A PCR product of the repeat region of the rOmp A gene from R. honei was amplified and calculated to contain 11 repeat units.

Antibodies, Bacterial↗
PubMed1997

Hypoglossal neuropraxia following endotracheal intubation.

A case of hypoglossal nerve neuropraxia following elective drainage of bilateral chronic subdural haematomas is described. We postulate that the cause of neuropraxia was inadvertent extubation of the trachea with the cuff inflated, leading to compression and stretch of the nerve against the greater horn of the hyoid bone. The literature on cranial nerve palsies following endotracheal intubation is reviewed.

Aged↗
PubMed1997

Effect of alteration of maternal plasma progesterone concentrations on fetal behavioural state during late gestation.

Placental progesterone synthesis exposes the fetus to high levels of progesterone and progesterone metabolites during late gestation which may influence fetal behaviour. To determine the role of maternal progesterone synthesis in the control of fetal arousal state and fetal breathing movements (FBM), the effect of raising and lowering maternal progesterone concentrations was examined in chronically catheterised fetal sheep. Fetal and maternal vascular catheters, fetal tracheal and amniotic fluid catheters as well as electrodes for recording fetal electrocortical (ECoG), electro-ocular (EOG) and nuchal muscle electromyographic (EMG) activity were implanted between 118 and 122 days gestational age (GA). Progesterone, 100 mg, administered twice daily i.m. for 3 days (130-133 days GA) resulted in a marked elevation in maternal plasma progesterone concentrations (370 +/- 121%, n = 5, P < 0.05), but had no effect on fetal plasma concentrations. Fetal EOG episodes and the duration of fetal behavioural arousal were significantly suppressed throughout the progesterone treatment period (74.4-81.1% and 58-65% respectively, P < 0.05, n = 5). Four ewes received Trilostane (25 mg i.v.), a 3 beta-hydroxysteroid dehydrogenase inhibitor, between 136 and 140 days GA. Maternal and fetal progesterone concentrations were significantly lowered by 60 min after treatment (19.8 +/- 8.0% and 39.5 +/- 24.3% respectively, P < 0.05). The incidence of fetal EOG activity increased from a pretreatment level of 26.8 +/- 1.5 min/h to 30.3 +/- 2.8 min/h at 1-6 h and to 35.0 +/- 1.7 min/h (P < 0.05) during the 7-12 h after Trilostane treatment. The duration of FBM episodes was significantly higher at 1-6 h and 7-12 h after Trilostane treatment (19.5 +/- 3.0 and 23.6 +/- 5.5 min/h respectively, P < 0.05) compared with pretreatment levels (11.2 +/- 1.2 min/h). We conclude that increasing maternal progesterone levels suppresses fetal EOG activity and behavioural arousal, whereas reducing maternal progesterone synthesis leads to an elevation of EOG activity and FBM.

3-Hydroxysteroid Dehydrogenases↗
PubMed1997

Transferring electronic medical records.

This article outlines the variety of computing environments, application systems and data structures that are available to the general practitioner. The transfer of data from and to electronic medical records systems will become more important as their use increases. Transferability requires the ability to match the data elements between the conversing application systems, and carry out a series of communication steps. Ways to ensure data element matching are described. The communications steps are delineated, and methods of achieving these steps briefly explained. The transfer methods proposed by the medical software industry of Australia are dealt with in detail. They involve the creation of an industry standard 'meta-record' which acts as a standard interface or gateway to the real record. The communication steps are carried out by a medical record 'agent', which is created and maintained by an independent organisation.

Australia↗
PubMed1997

Evidence for fusion between multilamellar endosomes and autophagosomes in HeLa cells.

The organelles of the endocytic and autophagic pathways were studied in HeLa cells using immunoelectron microscopy and stereological techniques. In the absence of autophagic stimulation, characteristic particulate structures containing closely packed layers of membrane received the fluid-phase marker horseradish peroxidase after 25 min uptake. These multilamellar endosomes contained the majority of the cellular immunogold labeling obtained by using a monoclonal antibody (1B5) directed against a lysosomal glycoprotein. Lysosomes with homogeneous dense content were only poorly labeled. After stimulation of autophagy, two classes of autophagosome profile appeared. One had a double limiting membrane and content that resembled the surrounding cytoplasm. The other most abundant type possessed a single limiting membrane and contained multilamellar structures which were strikingly similar to multilamellar endosomes, not only in form, but also in volume and membrane packing density. Immunogold labeling showed that now the majority of 1B5 labeling was located in the class of autophagosomes which contained multilamellar structures. Stereological methods showed that, after autophagic stimulation, multilamellar endosomes had become depleted, while multilamellar structures had appeared within the autophagosomes. Taken together, these data provide evidence that autophagosomes of HeLa cells fuse with preexisting multilamellar endosomes.

Autophagy↗
PubMed1997

Case study. Outcomes management in orthopaedics.

Improving outcomes while maintaining quality and satisfaction in today's healthcare environment is a challenge. This article shares some of the foundation work and the results of an interdisciplinary team effort toward that goal. Changes in care practices and their impact on outcomes can promote the welfare of the patient, institution, and the nation's health.

Hospital Charges↗